Menstrual Cycle Phases: The 4 Stages, Hormones & Fertile Days

The menstrual cycle has four phases: the menstrual phase (your period, about days 1 to 5), the follicular phase (days 1 to 13, when an egg matures), ovulation (around day 14, when the egg is released) and the luteal phase (days 15 to 28, when the womb prepares for a possible pregnancy). These days are for a 28-day cycle; any cycle from 21 to 35 days is normal, and the difference is almost always in the follicular phase. Knowing your phases helps you find your fertile days and spot when something is not right. At Yaal Fertility Centre in Chennai, Dr. Rukkayal Fathima and our team use this same map of the cycle to plan tests and fertility treatment.

The 4 Menstrual Cycle Phases at a Glance

Day 1 is the first day of full bleeding.

The follicular phase overlaps with your period, because follicles start growing while you are still bleeding.

The Hormones That Run the Cycle

• FSH (follicle-stimulating hormone) from the brain tells the ovaries to grow follicles, each holding an egg.
• Estrogen, made by the growing follicles, rebuilds the womb lining and makes cervical mucus sperm-friendly.
• LH (luteinising hormone) surges in mid-cycle and triggers the release of the egg.
• Progesterone, made by the empty follicle (the corpus luteum) after ovulation, prepares the lining for an embryo.

If any of these signals is disturbed, by PCOS, thyroid problems or high prolactin for example, the cycle becomes irregular. See hormonal imbalance symptoms in women.

Each Phase Explained

1. Menstrual Phase (Your Period)

If no pregnancy happened in the last cycle, progesterone and estrogen fall and the womb lining sheds. Bleeding usually lasts 3 to 7 days. Cramps come from the womb muscle contracting, driven by chemicals called prostaglandins. Tiredness and a low back ache are common.

2. Follicular Phase (Egg Growing)

From day 1, FSH stimulates a group of follicles. Usually one becomes the dominant follicle and the rest stop growing. As it grows, it makes more estrogen, which thickens the womb lining. Many women feel more energetic in this phase, and vaginal discharge gradually becomes wetter.

This is the phase that varies most in length. A woman with a 32-day cycle simply has a longer follicular phase than a woman with a 26-day cycle.

3. Ovulation (Egg Release)

When estrogen peaks, the brain releases a surge of LH, and the egg is released about 24 to 36 hours later. The egg survives for only 12 to 24 hours. Signs of ovulation include:

• Clear, slippery, stretchy discharge, like raw egg white.
• A mild ache on one side of the lower tummy.
• A positive LH (ovulation) kit.
• A small rise in body temperature the day after ovulation.

4. Luteal Phase (Getting Ready for Pregnancy)

After ovulation, the empty follicle becomes the corpus luteum and makes progesterone. The lining becomes soft and rich in nutrients, ready for an embryo. This phase is fairly fixed at about 12 to 14 days.

If an embryo implants, it makes hCG, which keeps progesterone high. If not, progesterone falls after about 14 days and your period starts. Breast tenderness, bloating and mood changes before a period are caused by these hormone shifts. Read about implantation symptoms and how they overlap with PMS.

What Discharge Looks Like in Each Phase

Cervical mucus changes with your hormones, and once you know the pattern it is one of the easiest free ways to follow your cycle.

Discharge that is green, grey, frothy, smells unpleasant or comes with itching or burning is not part of the normal cycle and may be an infection worth checking.

Mood, Energy and Exercise Across the Cycle

Many women notice that how they feel follows a monthly pattern. This varies from person to person, but a common picture is:

• During your period: lower energy and cramps. Gentle walking, stretching or yoga often ease cramps better than complete rest. Our guide to period pain relief covers more home remedies.
• Follicular phase: energy and mood usually lift as estrogen rises. Many women find this the easiest time for harder workouts.
• Around ovulation: energy is often at its peak and some women notice a higher sex drive.
• Luteal phase: as progesterone rises, some women feel more tired, hungry, bloated or irritable, especially in the last few days before the period (PMS).

Regular exercise across the whole month, steady meals with enough protein and fibre, and good sleep all reduce PMS symptoms. Very intense training combined with eating too little, however, can stop ovulation altogether, which is one reason athletes sometimes lose their periods.

If low mood, anxiety or irritability before your period is severe enough to affect work or relationships, talk to your doctor. This can be a treatable condition called premenstrual dysphoric disorder (PMDD).

Your Fertile Window

The fertile window is about 6 days: the 5 days before ovulation and the day of ovulation. Sperm can survive up to 5 days in fertile mucus, but the egg lasts only a day, so the best chances come from sex in the 2 to 3 days before ovulation.

How to Find Your Ovulation Day

Because the luteal phase is about 14 days long, count back 14 days from the day your next period is due.

Does Ovulation Always Happen on Day 14?

No. Day 14 is only true for a 28-day cycle, and even then ovulation can move by a few days from month to month. Stress, illness, travel and changes in sleep can all delay it. This is why counting days alone is a rough guide, and why real signs such as stretchy discharge or a positive LH kit are better clues to when you are fertile.

How Many Days After Your Period Can You Get Pregnant?

It depends on your cycle length. With a 5-day period:

• In a 26-day cycle, the fertile window opens about 2 days after your period ends.
• In a 28-day cycle, about 4 days after.
• In a 32-day cycle, about 8 days after.

With a very short cycle, the fertile window can even start before your period has finished. Our guide to the chances of getting pregnant by cycle day shows the odds for each day.

More Accurate Ways to Track Ovulation

• LH kits detect the surge a day or so before ovulation (less reliable in PCOS, see below).
• A follicular study uses a few ultrasound scans to watch the follicle grow and confirm that it has released an egg.
• A progesterone blood test about 7 days before your period (day 21 of a 28-day cycle) confirms whether you ovulated.

Our guide to the signs of ovulation explains how to use LH kits and chart your temperature step by step.

How to Track Your Cycle, Step by Step

Tracking for three months gives you, and your doctor, a clear picture of your own pattern.

1. Mark day 1 every month. Note the first day of full bleeding (not spotting) in a calendar or an app. Also note how many days you bleed and whether the flow is light, normal or heavy.
2. Work out your cycle length. Count from one day 1 to the next day 1. After three cycles, you will know your usual length and how much it varies.
3. Watch your discharge. Check once a day and note when it becomes clear and stretchy. The last day of this mucus is usually close to ovulation.
4. Add an LH kit if you are trying to conceive. Start testing a few days before you expect to ovulate (for a 28-day cycle, around day 10 or 11) and test once or twice a day until it turns positive.
5. Note symptoms. Cramps, breast tenderness, mood changes, spotting between periods or pain during sex are all useful to record.
6. Bring your notes to your appointment. A simple record of dates and symptoms often saves a lot of time in working out what is going on.

Period-tracking apps are convenient, but remember that their "fertile days" are predictions based on averages. If your cycles are irregular, or you have PCOS, an app's prediction can be several days out. Real signs, such as discharge and LH kits, or a scan, are more reliable.

When the Phases Go Wrong

If ovulation does not happen, there is no luteal phase and no progesterone. The lining keeps building under estrogen alone and sheds irregularly, giving late, unpredictable or heavy periods. Common reasons are:

• PCOS, the most common cause. See PCOS and fertility.
• Thyroid problems. See thyroid and fertility.
• High prolactin, stress, weight change or very intense exercise.
• Approaching menopause, when cycles first shorten and then become irregular.

A short luteal phase (under about 10 days) can also make it harder for an embryo to implant. For more on causes and tests, see irregular periods: causes and when to worry. Women who do not ovulate regularly can often be helped with ovulation induction.

PCOS and the Cycle Phases

In polycystic ovary syndrome (PCOS), the follicular phase is where things stall. Several follicles start to grow, but higher levels of androgens and insulin stop any one of them from maturing fully. Without a mature follicle, the LH surge and ovulation do not happen on time, so the luteal phase and its progesterone never begin.

The result is a long, unpredictable cycle: periods may come every six weeks, every few months, or stop for a while, and can be heavy when they arrive. LH kits can also mislead, because LH is often high all the time in PCOS. Treatment usually aims to restore ovulation, through weight and lifestyle changes, medicines, or ovulation induction with scan monitoring when you are trying to conceive. Read about our PCOS care.

How Your Cycle Changes Through Life

Teenage Years

In the first two to three years after periods start, cycles are often irregular because the link between the brain and ovaries is still maturing. Long gaps are common. Periods that are extremely heavy, very painful, or have not settled into a pattern after about three years are worth a check.

Twenties and Early Thirties

This is usually the most regular time. Cycles tend to settle into a steady length, and most women ovulate most months. A sudden change in pattern at this age, such as cycles becoming much longer, often has a cause worth finding, such as PCOS, a thyroid problem or weight change.

After Childbirth and While Breastfeeding

Breastfeeding raises prolactin, which holds back ovulation, so periods often stay away for months. When they return, the first few cycles may be irregular. Ovulation can happen before the first period comes back, so it is possible to conceive again before you have had a period.

Late Thirties and Forties

As the number of eggs falls, the follicular phase usually shortens first, so cycles become a few days shorter. Later, in the years before menopause, some cycles skip ovulation altogether and periods become irregular, sometimes heavier. Changes in egg quantity are reflected in the AMH test, which many women in their thirties use to plan ahead.

Which Tests Are Done on Which Cycle Day

Because hormones change through the month, fertility tests are timed to the cycle. If you are being investigated, your doctor may ask you to come in on particular days.

These tests are brought together in a female fertility evaluation.

When to See a Doctor

• Cycles regularly shorter than 21 days or longer than 35 days.
• No period for 3 months when you are not pregnant.
• Very heavy bleeding, bleeding between periods, or severe period pain.
• Trying to conceive for 12 months, or 6 months if you are over 35. See when to see a fertility specialist.